This invention concerns a tap and a mixer for the delivery and mixing of water by using a particular push-button control, that is to say a tap for sanitary, public, domestic or industrial plants, with one or more than one shutter, pushed to open by a push-button against the action of a spring. The invention relates, more particularly, to such an apparatus which includes a mixer consisting of at least two taps (one for hot and one for cold water) with a push-button control, and of a possible deviating element, as well equipped with a push-button control for the delivery of water in two different delivery pipes at choice (tub or shower).
The state of art includes a type of tap with push-button, equipped with a cylindrical shutter with a rubber washer on its surface towards the shutter seat, which is coaxial with the control shaft of the shutter, that is to say with a ring-shaped seal. The shutter is fastened to the end of a shaft, the opposite end of which is formed by the push-button control; in order to draw water it is necessary not only to overcome the action of a spring but, above all, the strong thrust due to the water pressure in the waterworks; such a tap is generally applied only to fountains, as it requires a considerable effort, which can be made only with the palm of the hand or with the thumb of an adult person.
This prior state of art is amenable to further improvements. A cylindrical shutter equipped with the ring-shaped seal must have a considerable diameter according to the rate of flow to be delivered due to the need to have a large annular opening around the shutter shaft, sufficient for the delivery of the large quantity of water generally required; this requires a large base area of the shutter cylinder with the result that a strong thrust is needed, the value of which is determined by the value of the water pressure in the water works, multipled by the value of the shutter area. For instance, if the shutter has a diameter of 16 mm, its area is approximately 2.5 cm.sup.2, which--in the normal case of approximately 30 N/cm.sup.2 of pressure in the water works--requires a thrust of 75 N more than that of the spring.
From the aforesaid it is evident that such a tap can be operated only by a person with sufficient strength and certainly not by a sick or old person or by a child; therefore, taps that can be operated by means of a push-button have not been used for any domestic purpose.
From the aforesaid state of the art derives the need to solve the technical problem of finding a shutter than can be operated by means of a push-button by any person, even with rather limited strength, that is to say a shutter moved by means of a push-button, requiring a small thrust for its opening, even inferior to 10 N. Thus, in the case of small rates of flow, this thrust might at the utmost be reduced to the value of just a few Newton or less and thus allow the use of the tap also in domestic sanitary plants, where it must be suitable for continuous use also by old and sick persons or children.